SOFTDEVICE: INVALID MEMORY ACCESS

[Muqarrab]

Hi, 

I am working on ble_app_template.
I am trying to save a value in the flash memory of nRF52840.
I am using the following 2 functions to write/read in flash memory but getting this error.

SOFTDEVICE: INVALID MEMORY ACCESS

I am using this memory as a starting memory to save values.(As mentioned in this link:  Flash - Non-volatile memory)

uint32_t f_addr = 0x4001E001;

Any solution for this error? 
Thanks

uint32_t f_addr = 0x4001E001; 


// Create a pointer to that address
uint32_t * p_addr = &f_addr; 

uint32_t val = 123456; 

void write_T()
{
    nrf_nvmc_write_word(f_addr, val);
}

void read_T()
{
     NRF_LOG_INFO("The Data read from flash is: %d", *(p_addr));
}

[haakonsh]

An address of 0x4001E001 is in the peripheral address space(ACL — Access control lists to be specific), not flash.

See Memory map. 

You should also use the SoftDevice's flash API: sd_flash_write and sd_flash_page_erase.

[Muqarrab]

Hi haakonsh,
Then from which memory I can start memory?
(I have to save ~20 bytes)
Thanks!

[Muqarrab]

Is this the right way to write/read data in flash memory?
In this case when I read data it shows->


<info> app: The Data read from flash is: 1044480

uint32_t f_addr = 0x000FF000; 


// Create a pointer to that address
uint32_t * p_addr = &f_addr; 

uint32_t val = 123456; 

void write_T()
{
    nrf_nvmc_write_word(f_addr, val);
}

void read_T()
{
     NRF_LOG_INFO("The Data read from flash is: %d", *(p_addr));
}

[haakonsh]

uint32_t f_addr = 0x000FF000; 


// Create a pointer to that address
uint32_t * p_addr = (uint32_t *)f_addr; //cast f_addr to a pointer

uint32_t val = 123456; 

uint32_t write_T()
{
    return sd_flash_write(p_addr, &val, sizeof(val));
}

uint32_t erase_T()
{
    return sd_flash_page_erase(255);
}

void read_T()
{
     NRF_LOG_INFO("The Data read from flash is: %d", *(p_addr));
}

[Muqarrab]

Hi haakonsh,
I have implemented your code and get the following error.




So I changed it as below.

// Create a pointer to that address
uint32_t * p_addr = &f_addr; 

Now I want to read data I have saved(123456) but when I called void read_T() I get always this. (I want data I have written that address.)

<info> app: The Data read from flash is: 1044480

[haakonsh]

In hex that's 0xFF000, the value of p_addr. 

When you dereference p_addr it will contain the value of f_addr, and not the data in flash at address 0x000FF000. You need treat p_addr as a double, not single pointer.

const uint32_t f_addr = 0x000FF000; 


// Create a pointer to that address
//initialization value must be const
uint32_t * p_addr = (uint32_t *)f_addr; //cast f_addr to a pointer

uint32_t val = 123456; 

uint32_t write_T()
{
    return sd_flash_write(p_addr, &val, sizeof(val));
}

uint32_t erase_T()
{
    return sd_flash_page_erase(255);
}

void read_T()
{
    // dereference the pointer that p_addr points to
    NRF_LOG_INFO("The Data read from flash is: %u", *(uint32_t *)*(p_addr));
}